1. Field of the Invention
The present invention relates to a semiconductor wafer inspection tool and a semiconductor wafer inspection method for inspecting a substrate apparatus which has a circuit pattern such as a semiconductor apparatus and liquid crystal using electron beams.
2. Background Art
Conventionally, an electron beam based pattern inspection tool is known which irradiates electron beams onto a wafer to be inspected, detects secondary electrons generated and scans electron beams, thereby obtains a secondary electron image of the circuit pattern on the wafer, compares the detected image with a reference image which must have an identical pattern and judges locations where there is a large difference as defects (e.g., see JP Patent Publication (Kokai) No. 1′-160247A (1999)).
The material and construction forming a circuit pattern to be inspected by an inspection tool are becoming increasingly complicated and defects are also becoming more diversified accordingly. The conventional inspection tools create various detection conditions by appropriately setting an acceleration voltage which represents energy of electron beams on a wafer and electric field intensity or the like on the object.
As will be described more specifically later, as for electron optical systems in particular, there are modes of setting the electron optical systems called an “NVC” (Negative Voltage Contrast) mode and a “PVC” (Positive Voltage Contrast) mode. Since the NVC mode and the PVC mode have substantially different types of detectable defects, there is a demand for an apparatus which can singly make inspection performance in these two modes compatible with each other. On the other hand, however, an optimal configuration of an electron optical system to realize these two modes varies greatly and it is difficult for a single optical system to realize the optimal configuration for both conditions.
The present invention has been implemented in view of such circumstances and it is an object of the present invention to provide a semiconductor wafer inspection tool and a semiconductor wafer inspection method capable of performing inspections under appropriate conditions in any mode of the NVC mode and the PVC mode.